Expression of endothelial nitric oxide synthase in the postnatal developing porcine kidney

The postnatal pattern of renal endothelial nitric oxide synthase (eNOS) is unknown. The purpose of this study was to characterize eNOS expression during maturation and compare this to neuronal NOS (nNOS). The experiments measured whole kidney eNOS mRNA expression by RT-PCR and protein content by Western blot, as well as cortical and medullary protein content in piglets at selected postnatal ages and in adult pigs. Whole kidney eNOS mRNA was compared with nNOS. Whole kidney eNOS expression decreased from the newborn to its lowest at 7 days, returning by 14 days to adult levels. This eNOS mRNA pattern contrasted with nNOS, which was highest at birth, and progressively decreased to its lowest level in the adult. At birth, cortical eNOS protein was greater than medullary, contrasting with the adult pattern of equivalent levels. In conclusion eNOS is developmentally regulated during early renal maturation and may critically participate in renal function during this period. The eNOS developmental pattern differs from nNOS, suggesting that these isoforms may have different regulatory factors and functional contributions in the postnatal kidney.

Role of ecNOS-derived NO in mediating TNF-induced endothelial barrier dysfunction

We tested the hypothesis that endothelial cell nitric oxide synthase (ecNOS) mediates the tumor necrosis factor (TNF)-alpha-induced increase in nitric oxide (NO) and albumin permeability in pulmonary microvessel endothelial monolayers (PEM). PEM lysates were analyzed for ecNOS mRNA (RT-PCR), ecNOS protein (Western immunoblot), NO levels (NO, the oxidation product of NO), and barrier function (albumin clearance rate). PEM were incubated with TNF (50 ng/ml) for 0.5, 2, 4, and 24 h. TNF induced a decrease in ecNOS mRNA at 2, 4, and 24 h. TNF induced an acute (0.5 h) increase followed by a protracted decrease (4-24 h) in ecNOS protein levels. The other NOS isotypes, inducible and brain NOS, could not be detected in the PEM using RT-PCR and Western blot assay. ecNOS antisense oligonucleotide decreased ecNOS protein, which prevented the increase in NO and albumin permeability at TNF-4 h. Spermine-NONOATE, the NO agonist, ablated the protective effect of ecNOS antisense oligonucleotide on albumin permeability in response to TNF-4 h. However, ecNOS antisense oligonucleotide had no effect on the TNF-induced increase in albumin permeability at 24 h despite prevention of the increase in NO. The data indicate that the isotype ecNOS mediates generation of NO and the acute (i.e., 4 h) barrier dysfunction; however, the prolonged (i.e., 24 h) increase in the TNF-induced increase in endothelial permeability is independent of NO.

Role of astrocytes in pathogenesis of ischemic brain injury

Astrocytes play an important role in the homeostasis of the CNS both in normal conditions and after ischemic injury. The swelling of astrocytes is observed during and several seconds after brain ischemia. Then ischemia stimulates sequential morphological and biochemical changes in glia and induces its proliferation. Reactive astrocytes demonstrate stellate morphology, increased glial fibrillary acidic protein (GFAP) immunoreactivity, increased number of mitochondria as well as elevated enzymatic and non-enzymatic antioxidant activities. Astrocytes can re-uptake and metabolize glutamate and in this way they control its extracellular concentration. The ability of astrocytes to protect neurons against the toxic action of free radicals depends on their specific energy metabolism, high glutathione level, increased antioxidant enzyme activity (catalase, superoxide dismutase, glutathione peroxidase) and overexpression of antiapoptotic bcl-2 gene. Astrocytes produce cytokines (TNF-alpha, IL-1, IL-6) involved in the initiation and maintaining of immunological response in the CNS. In astrocytes, like in neurones, ischemia induces the expression of immediate early genes: c-fos, c-jun, fos B, jun B, jun D, Krox-24, NGFI-B and others. The protein products of these genes modulate the expression of different proteins, both destructive ones and those involved in the neuroprotective processes.

Decreased renal expression of nitric oxide synthase isoforms in adrenocorticotropin-induced and corticosterone-induced hypertension

Administration of adrenocorticotropic hormone (ACTH) leads to the development of hypertension. Because glucocorticoids can affect the nitric oxide system at several sites, the present study tested the hypothesis that nitric oxide synthase (NOS) expression may be altered in ACTH-induced and corticosterone-induced hypertension in the rat. This was addressed by measuring Nos1, Nos2, and Nos3 mRNA in the kidney, adrenal gland, heart, and hypothalamus of 16 ACTH-treated and 16 vehicle-treated rats as well as in 10 corticosterone-treated and 10 control rats. In addition, in situ hybridization and immunohistochemistry were used to confirm changes by detection of Nos in RNA and NOS protein in tissues. Systolic blood pressure of ACTH and corticosterone rats was elevated (165+/-6 and 162+/-11 mm Hg; P<0.001 versus control). Each Nos isoform mRNA was measured by reverse transcriptase-polymerase chain reaction technique. In ACTH rats, mRNA for Nos2 was reduced in renal cortex by 58+/-5% and in medulla by 68+/-7%; for Nos3, mRNA reductions of 59+/-6% and 51+/-11% were seen (P<0.001 after Hochberg correction for multiple comparisons). In corticosterone rats, Nos2 mRNA decreased in cortex by 68+/-5% and in medulla by 62+/-6%; Nos3 mRNA by 50+/-8% in cortex, and Nos1 by 29+/-7% in medulla (all P<0.001 after Hochberg correction). Reductions seen in kidney were supported by in situ hybridization and immunohistochemistry. Apart from a 62+/-2% decrease in Nos2 mRNA in adrenal of ACTH rats (corrected P<0.05), no significant changes were seen in the other nonrenal tissues for any isoform. In conclusion, we have shown for the first time that the physiological components of glucocorticoid action (ACTH and corticosterone) when given chronically in vivo reduce Nos2 and Nos3 expression in the kidney. Such changes are consistent with a role in hypertension for ACTH and corticosterone.

Transcriptional complexity of the Anopheles stephensi nitric oxide synthase gene

Anopheles stephensi nitric oxide synthase (AsNOS) is a single copy gene that shares significant structural homology with the three human NOS genes and is inducibly expressed in Plasmodium-infected mosquitoes. Exon-specific Northern analyses and exon-spanning polymerase chain reaction amplification were used to further characterize transcription from this gene. A total of 18-22 AsNOS transcripts, ranging in size from 1.0 to 7.5 kb, were detected in replicated Northern blots from three separate cohorts of mosquitoes. Three transcripts (1604, 2330, and 2585 bp) were significantly induced in Plasmodium-infected mosquitoes (p<0.05), while others showed varying patterns of induction or downregulation. Five splice variants contained deletions of 1-7 exons. All but one deletion pattern was predicted to introduce in-frame stop codons or alter the translational reading frame. A novel insertion derived from intron sequence was predicted to introduce in-frame stop codons following exon 11. Two truncated novel exon 1 variants were identified that are homologous to a previously published 5' sequence for this exon. The large number of AsNOS transcripts and diversity in AsNOS splicing and exon 1 sequences indicate that transcriptional complexity is a hallmark of both invertebrate and vertebrate NOS genes.

Aging-related expression of inducible nitric oxide synthase and markers of tissue damage in the rat penis

Erectile dysfunction in the aging male results in part from the loss of compliance of the corpora cavernosal smooth muscle due to the progressive replacement of smooth muscle cells by collagen fibers. We have examined the hypothesis that a spontaneous local induction of inducible nitric oxide synthase (iNOS) expression and the subsequent peroxynitrite formation occurs in the penis during aging and that this process is accompanied by a stimulation of smooth muscle apoptosis and collagen deposition. The penile shaft and crura were excised from young (3-5 mo old) and old (24-30 mo old) rats, with or without perfusion with 4% formalin. Fresh tissue was used for iNOS and proteasome 2C mRNA determinations by reverse transcription polymerase chain reaction assay, ubiquitin mRNA by Northern blot, and iNOS protein by Western blot. Penile sections from perfused animals were embedded in paraffin and immunostained with antibodies against iNOS and nitrotyrosine, submitted to the TUNEL assay for apoptosis, or stained for collagen, followed by image analysis quantitation. A 4.1-fold increase in iNOS mRNA was observed in the old versus young tissues, paralleled by a 4.9-fold increase in iNOS protein. The proteolysis marker, ubiquitin, was increased 1.9-fold, whereas a related gene, proteasome 2c, was not significantly affected. iNOS immunostaining was increased 3.6-fold in the penile smooth muscle of the old rats as compared with the young rats. The peroxynitrite indicator nitrotyrosine was increased by 1.6-fold, accompanied by a 3.6-fold increase in apoptotic cells and a 2.0-fold increase in collagen fibers in the old penis. In conclusion, aging in the penis is accompanied by an induction of iNOS and peroxynitrite formation that may lead to the observed increase in apoptosis and proteolysis and may counteract a higher rate of collagen deposition in the old penis.

Nitric oxide and the regulation of gene expression

During the past 15 years, nitric oxide (NO) and NO synthases have become an important research topic in cellular and molecular biology. NO is produced by many if not all mammalian cells and fulfils a broad spectrum of signaling functions in physiological and pathophysiological processes. In this review, recent advances in our understanding of the mechanisms by which NO regulates the expression of eukaryotic genes will be summarized. The currently available data illustrate that NO has multiple molecular targets: it can not only directly influence the activity of transcription factors but also modulates upstream signaling cascades, mRNA stability and translation, as well as the processing of the primary gene products.

Intervention du monoxyde d'azote, NO, et de ses dérivés oxydés, particulièrement chez les mammifères

Nitric oxide (NO) is a natural and stable free radical produced in soil and water by the bacteriological reduction of nitrites and nitrates and in animals by the enzyme oxidation of L-arginine. NO is biosynthesised by finely regulated enzymatic systems called NO-synthases and readily diffuses through tissues. It reacts rapidly with hemoproteins and iron-sulphur centers to form nitrosylated compounds. It oxidises more slowly to form nitrogen oxides that nitrosate thiols into thionitrite. NO is transported in these various forms and released spontaneously or through yet unclear mechanisms into most cells; it also regulates oxygen consumption at the mitochondrial respiratory chain level through interaction with cytochrome oxidase. In the cardiovascular system, NO lowers blood pressure by activating a hemoprotein, the guanylate cyclase present in muscle cells; through such interaction it acts also as a neuromediator and neuromodulator in the nervous system. However, many of NO's roles result from rapid coupling to other radicals; for example, it reacts with the superoxide anion (O–2) to form oxoperoxinitrate (ONOO–, also known as peroxynitrite). This strong oxidant of metallic centers, thiols, and antioxidants is also able to convert tyrosine to 3-nitrotyrosine and to act upon tyrosine residues contained in proteins. The biological aspects of the roles of NO are presented with particular respect to the rapid interactions of NO with hemoproteins' iron and other radicals. Concurrently, NO oxidation enables nitrosation reactions primarily of thiols but ultimately of nucleic bases. The thionitrite function (R-S-NO) thus formed and the dimerisation and nitration of tyrosine residues are protein post-translational modifications that are being investigated in animals.Key words: nitric oxide, peroxynitrite, nitration, nitrosation, nitrosylation. [Translated by the editors.]

Increased expression of endothelin-1 and inducible nitric oxide synthase isoform II in aging arteries in vivo: implications for atherosclerosis

We here report that aging increases expression of endothelin-1 and NO synthases in the vasculature and kidney of normotensive rats in vivo. Expression of preproendothelin-1 mRNA was quantified by RT-PCR and in situ hybridization, and endothelin-1 protein was determined by radioimmunoassay/HPLC. Vascular mRNA expression of NO synthase isoforms II and III was analyzed by RT-PCR. In young animals, vascular endothelin-1 protein was differentially expressed (aorta < renal artery < carotid artery) and increased with aging in all vascular beds (P < 0.05). In the intact aorta of aged rats, mRNA expression of preproendothelin-1, "inducible" NO synthase II, and endothelial cell NO synthase III gene was up-regulated (P < 0.05). Moreover, preproendothelin-1 mRNA expression increased in glomeruli and tubulointerstitial cells (P < 0.05). To our knowledge this is the first study demonstrating local vascular up-regulation of the trophic factor endothelin under physiological conditions. Activation of vascular endothelin and NO synthases may be important, pressure-independent factors contributing to structural and functional abnormalities of age-dependent diseases, including atherosclerosis.

Heregulin upregulates the expression of nitric oxide synthase (NOS)-1 in rat cerebellar granule neurons via the ErbB4 receptor

Heregulin plays key roles in regulating cell number, determining fate and establishing pattern in the developing nervous system via specific receptors (ErbBs), including ErbB4. Two recent reports have shown that ErbB4 forms a complex with postsynaptic density proteins, which are, in turn, known to complex with nitric oxide synthase (NOS)-1. To reveal whether heregulin might regulate the expression of NOS-1, cultures enriched in cerebellar granule cells were exposed to heregulin for 72 h. This treatment resulted in an increase in NOS-1 protein (> 70%), an effect mediated by the ErbB4 receptor. While nitric oxide might mediate some of the downstream effects of heregulin in the nervous system, heregulin treatment neither enhanced granule cell survival, nor protected neurons from acute glutamate excitotoxicity.

NOSIP, a novel modulator of endothelial nitric oxide synthase activity

Production of nitric oxide (NO) in endothelial cells is regulated by direct interactions of endothelial nitric oxide synthase (eNOS) with effector proteins such as Ca2+-calmodulin, by posttranslational modifications such as phosphorylation via protein kinase B, and by translocation of the enzyme from the plasma membrane caveolae to intracellular compartments. Reversible acylation of eNOS is thought to contribute to the intracellular trafficking of the enzyme; however, protein factor(s) that govern the translocation of the enzyme are still unknown. Here we have used the yeast two-hybrid system and identified a novel 34 kDa protein, termed NOSIP (eNOS interacting protein), which avidly binds to the carboxyl-terminal region of the eNOS oxygenase domain. Coimmunoprecipitation studies demonstrated the specific interaction of eNOS and NOSIP in vitro and in vivo, and complex formation was inhibited by a synthetic peptide of the caveolin-1 scaffolding domain. NO production was significantly reduced in eNOS-expressing CHO cells (CHO-eNOS) that transiently overexpressed NOSIP. Stimulation with the calcium ionophore A23187 induced the reversible translocation of eNOS from the detergent-insoluble to the detergent-soluble fractions of CHO-eNOS, and this translocation was completely prevented by transient coexpression of NOSIP in CHO-eNOS. Immunofluorescence studies revealed a prominent plasma membrane staining for eNOS in CHO-eNOS that was abolished in the presence of NOSIP. Subcellular fractionation studies identified eNOS in the caveolin-rich membrane fractions of CHO-eNOS, and coexpression of NOSIP caused a shift of eNOS to intracellular compartments. We conclude that NOSIP is a novel type of modulator that promotes translocation of eNOS from the plasma membrane to intracellular sites, thereby uncoupling eNOS from plasma membrane caveolae and inhibiting NO synthesis.

Shear stress-dependent regulation of the human beta-tubulin folding cofactor D gene

The flowing blood generates shear stress at the endothelial cell surface. The endothelial cells modify their phenotype by alterations in gene expression in response to different levels of fluid shear stress. To identify genes involved in this process, human umbilical vein endothelial cells were exposed to laminar shear stress (venous or arterial levels) in a cone-and-plate apparatus for 24 hours. Using the method of RNA arbitrarily primed polymerase chain reaction, we cloned a polymerase chain reaction fragment representing an mRNA species downregulated by arterial compared with venous shear stress (shear stress downregulated gene-1, SSD-1). According to Northern blot analysis, corresponding SSD-1 cDNA clones revealed a similar, time-dependent downregulation after 24 hours of arterial shear stress compared with venous shear stress or static controls. Three SSD-1 mRNA species of 2.8, 4.1, and 4.6 kb were expressed in a tissue-specific manner. The encoded amino acid sequence of the human endothelial SSD-1 isoform (4.1-kb mRNA species) revealed 80.4% identity and 90.9% homology to the bovine ss-tubulin folding cofactor D (tfcD) gene. Downregulation of tfcD mRNA expression by shear stress was defined at the level of transcription by nuclear run-on assays. The tfcD protein was downregulated by arterial shear stress. The shear stress-dependent downregulation of tfcD mRNA and protein was attenuated by the NO synthase inhibitor Nomega-nitro-L-arginine methyl ester. Furthermore, the NO donor DETA-NO downregulated tfcD mRNA. Because tfcD was shown to be a microtubule-destabilizing protein, our data suggest a shear stress-dependent regulation of the microtubular dynamics in human endothelial cells.

Anesthetic concentrations of riluzole inhibit neuronal nitric oxide synthase activity, but not expression, in the rat hippocampus

We hypothesized that anesthetic dose of riluzole, an inhibitor of glutamate neurotransmission, may affect the activity and/or expression of neuronal NOS (nNOS). Riluzole, N(G)-nitro-L-arginine-methyl ester (L-NAME) and 7-nitro indazole (7-NI) produced a concentration-related inhibition of nNOS activity in vitro. Riluzole competed with 7-NI for inhibition of nNOS activity, but had no effect on nNOS or endothelial NOS (eNOS) protein expression. Also, nNOS activity was significantly decreased in riluzole-anesthetized rats (40 mg kg(-1) i.p., -32+/-6% from controls, P<0.05). Therefore, blockade of nNOS activity may be involved in the anesthetic effects of riluzole in vivo.

Role of nitric oxide in the pathogenesis of chronic pulmonary hypertension

Chronic pulmonary hypertension is a serious complication of a number of chronic lung and heart diseases. In addition to vasoconstriction, its pathogenesis includes injury to the peripheral pulmonary arteries leading to their structural remodeling. Increased pulmonary vascular synthesis of an endogenous vasodilator, nitric oxide (NO), opposes excessive increases of intravascular pressure during acute pulmonary vasoconstriction and chronic pulmonary hypertension, although evidence for reduced NO activity in pulmonary hypertension has also been presented. NO can modulate the degree of vascular injury and subsequent fibroproduction, which both underlie the development of chronic pulmonary hypertension. On one hand, NO can interrupt vascular wall injury by oxygen radicals produced in increased amounts in pulmonary hypertension. NO can also inhibit pulmonary vascular smooth muscle and fibroblast proliferative response to the injury. On the other hand, NO may combine with oxygen radicals to yield peroxynitrite and other related, highly reactive compounds. The oxidants formed in this manner may exert cytotoxic and collagenolytic effects and, therefore, promote the process of reparative vascular remodeling. The balance between the protective and adverse effects of NO is determined by the relative amounts of NO and reactive oxygen species. We speculate that this balance may be shifted toward more severe injury especially during exacerbations of chronic diseases associated with pulmonary hypertension. Targeting these adverse effects of NO-derived radicals on vascular structure represents a potential novel therapeutic approach to pulmonary hypertension in chronic lung diseases.

Inhibition of small G proteins of the rho family by statins or clostridium difficile toxin B enhances cytokine-mediated induction of NO synthase II

In order to investigate the involvement of Ras and/or Rho proteins in the induction of the inducible isoform of nitric oxide synthase (NOS II) we used HMG-CoA reductase inhibitors (statins) and Clostridium difficile toxin B (TcdB) as pharmacological tools. Statins indirectly inhibit small G proteins by preventing their essential farnesylation (Ras) and/or geranylgeranylation (Rho). In contrast, TcdB is a glucosyltransferase and inactivates Rho-proteins directly. Human A549/8- and DLD-1 cells as well as murine 3T3 fibroblasts were preincubated for 18 h with statins (1 - 100 microM) or TcdB (0.01-10 ng ml(-1)). Then NOS II expression was induced by cytokines. NOS II mRNA was measured after 4 - 8 h by RNase protection assay, and NO production were measured by the Griess assay after 24 h. Statins and TcdB markedly increased cytokine-induced NOS II mRNA expression and NO production. Statin-mediated enhancement of NOS II mRNA expression was reversed almost completely by cotreatment with mevalonate or geranylgeranylpyrophosphate. It was only slightly reduced by farnesylpyrophosphate. Therefore, small G proteins of the Rho family are likely to be involved in NOS II induction. In A549/8 cells stably transfected with a luciferase reporter gene under the control of a 16 kb fragment of the human NOS II promoter (pNOS2(16)Luc), statins produced only a small increase in cytokine-induced NOS II promoter activity. In contrast, statins had a considerable superinducing effect in DLD-1 cells stably transfected with pNOS2(16)Luc. In conclusion, our studies provide evidence that statins and TcdB potentiate cytokine-induced NOS II expression via inhibition of small G proteins of the Rho family. This in turn results in an enhanced NOS II promoter activity and/or a prolonged NOS II mRNA stability.

Distinct subcellular localization and mRNA expression of neuronal nitric oxide synthase in the nucleus dorsalis and red nucleus and their correlation with inducible transcription factors after spinal cord hemisection

We previously reported on the differential expression of neuronal nitric oxide synthase (nNOS) in neurons of the nucleus dorsalis (ND) and red nucleus (RN), as well as differential roles of nitric oxide (NO) in these two distinct groups' neurons characterized with different nNOS phenotypes after lower thoracic spinal cord hemisection. To further understand the enzyme, nNOS expression was studied at the subcellular and mRNA levels by using electron microscopic immunohistochemistry (EM-IHC) and in situ hybridization respectively. Possible transcriptional regulation by c-Jun or CREB in the differential nNOS expression in both ND and RN neurons was also studied. nNOS mRNA was not found in the normal ND neurons, but was shown in the normal RN neurons. After spinal cord hemisection, nNOS mRNA was induced in the ipsilateral ND, while upregulated on both sides of the RN, which preceded protein induction or upregulation. By EM-IHC, nNOS immunoreaction products were predominantly bound to the membrane of the mitochondria, rough endoplasmic reticulum (rER), Golgi apparatus, and nuclear envelope in the RN neurons of normal rats as well as rats subjected to spinal cord hemisection. In contrast, nNOS-immunoreactive deposits in the experimental ND neurons were found to be mainly granular, being dispersed throughout the cytoplasmic matrix. It is speculated that the differential subcellular localizationof nNOS indicates that axotomy may trigger different nNOS transcripts and lead to different nNOS isoform expression in the normally non-nNOS- and normally nNOS-containing neurons. c-Jun was induced in the ipsilateral ND neuronsand upregulated only in the contralateral RN neurons. Activation of CREB by phosphorylation was occasionally detectable in the ND neurons, but not in the RN neurons. Double-labeling data showed a large proportion of c-Jun and nNOS colocalization in neurons of the ipsilateral ND and contralateral RN after spinal cord hemisection. However, dissociation of nNOS expression kinetics with c-Jun was observed in the ipsilateral RN. The results implied that nNOS expression might not be under the direct transcriptional regulation by c-Jun, although it seemed to be closely related to the c-Jun expression.

Expression of penile neuronal nitric oxide synthase variants in the rat and mouse penile nerves

Penile erection is mediated by nitric oxide (NO) synthesized by the neuronal nitric oxide synthase (nNOS). In the rat penis, the main nNOS mRNA variant, PnNOS, differs from cerebellar nNOS (CnNOS) by a 102 base pair insert encoding a 34-amino acid sequence. In the mouse, two nNOS mRNAs have been identified: nNOSalpha, encoding a 155-kDa protein, and an exon 2-deletion variant, nNOSbeta, encoding a 135-kDa protein that lacks a domain where a protein inhibitor of nNOS (PIN) binds. We wished to determine whether PnNOSalpha and beta are expressed in the rat penis and are located in the nerves and whether the beta form persists in the potent nNOS knock-out mouse (nNOS( big up tri, open big up tri, open)). A PnNOS antibody against the insert common to both PnNOSalpha and beta detected the expected 155-kDa protein in PnNOSalpha-transfected cells. This antibody, and the one common to PnNOS/CnNOS, showed (on Western blots) the 155- and 135-kDa nNOS variants in rat penile tissue during development and aging. PnNOSalpha mRNA and its subvariants were found as the main nNOS in the penile corpora, the cavernosal nerve, and the pelvic ganglia, with lower levels of PnNOSbeta mRNA. In tissue sections, PnNOS protein was immunodetected in the penile nerve endings in the rat and in the nNOS wild-type and nNOS( big up tri, open big up tri, open) mice. An antibody against the sequence encoded by exon 2 did not react (on Western blots) with the 135-kDa band, which confirms that this protein is the beta form. In conclusion, both PnNOSalpha and beta are expressed in the rat penis at all ages and are located in the nerves. The beta form may allow nitric oxide synthesis during erection to be partially insensitive to PIN. The residual expression of PnNOS, and possibly CnNOS, in the penis of the nNOS( big up tri, open big up tri, open) mouse occurs through transcription of the beta mRNA, and this may explain the retention of erectile function when the expression of nNOSalpha is disrupted.

Complex contribution of the 3'-untranslated region to the expressional regulation of the human inducible nitric-oxide synthase gene. Involvement of the RNA-binding protein HuR

Cytokine stimulation of human DLD-1 cells resulted in a marked expression of nitric-oxide synthase (NOS) II mRNA and protein accompanied by only a moderate increase in transcriptional activity. Also, there was a basal transcription of the NOS II gene, which did not result in measurable NOS II expression. The 3'-untranslated region (3'-UTR) of the NOS II mRNA contains four AUUUA motifs and one AUUUUA motif, known to destabilize the mRNAs of proto-oncogenes, nuclear transcription factors, and cytokines. Luciferase reporter gene constructs containing the NOS II 3'-UTR showed a significantly reduced luciferase activity. The embryonic lethal abnormal vision (ELAV)-like protein HuR was found to bind with high affinity to the adenylate/uridylate-rich elements of the NOS II 3'-UTR. Inhibition of HuR with antisense constructs reduced the cytokine-induced NOS II mRNA, whereas overexpression of HuR potentiated the cytokine-induced NOS II expression. This provides evidence that NOS II expression is regulated at the transcriptional and post-transcriptional level. Binding of HuR to the 3'-UTR of the NOS II mRNA seems to play an essential role in the stabilization of this mRNA.

Citrulline immunohistochemistry for demonstration of NOS activity in vivo and in vitro

Nitric oxide (NO), a biomolecule with major cytotoxic potency, is generated by NO synthases (NOS) utilizing l-arginine as substrate and citrulline is formed as a "side product." In brain tissue, citrulline is considered to be produced exclusively by NOS, due to the incomplete urea cycle in the brain. We aimed to characterize NOS activity by citrulline immunostaining in different cell types of the brain under in situ conditions and in slice and culture experiments. NOS-positive neurons and activated microglial cells were the most prominent citrulline-positive structures. Lack of citrulline immunoreaction in neurons of nNOS knockout mice emphasizes the dependency of citrulline positivity on NOS activity, and likewise there was no citrulline staining after application of the NOS inhibitors 7-nitroindazole and NIL. Interestingly, only a portion of NOS-containing neurons costained for citrulline. The inhibition of argininosuccinate synthetase by alpha-methyl-dl-aspartate increased the number of citrulline-positive cells, apparently due to reduction of the turnover rate of citrulline. Cells positive for NOS but negative for citrulline may indicate that the enzyme is either not activated or inhibited by cellular control mechanisms. The fact that not all citrulline-positive cells were NOS positive may be explained by an insufficient detection sensitivity or by disparate sites of citrulline production and recycling. The present results show that citrulline immunocytochemistry offers a viable and convenient means for studying NOS activity at the single-cell level to elicit its posttranslational control under physiological and pathophysiological conditions.

Dynamic regulation of neuronal NO synthase transcription by calcium influx through a CREB family transcription factor-dependent mechanism

Neuronal nitric oxide (NO) synthase (nNOS) is dynamically regulated in response to a variety of physiologic and pathologic stimuli. Although the dynamic regulation of nNOS is well established, the molecular mechanisms by which such diverse stimuli regulate nNOS expression have not yet been identified. We describe experiments demonstrating that Ca(2+) entry through voltage-sensitive Ca(2+) channels regulates nNOS expression through alternate promoter usage in cortical neurons and that nNOS exon 2 contains the regulatory sequences that respond to Ca(2+). Deletion and mutational analysis of the nNOS exon 2 promoter reveals two critical cAMP/Ca(2+) response elements (CREs) that are immediately upstream of the transcription start site. CREB binds to the CREs within the nNOS gene. Mutation of the nNOS CREs as well as blockade of CREB function results in a dramatic loss of nNOS transcription. These findings suggest that nNOS is a Ca(2+)-regulated gene through the interactions of CREB on the CREs within the nNOS exon 2 promoter and that these interactions are likely to be centrally involved in the regulation of nNOS in response to neuronal injury and activity-dependent plasticity.

Ontogeny of neuronal nitric oxide synthase, NOS I, in the developing porcine kidney

To determine if the developing kidney differs from the adult in the expression of the neuronal nitric oxide synthase, NOS I, these experiments measured mRNA gene expression by RNase protection assay and protein content by Western blot of NOS I in piglets at ages newborn and 3, 7, 10, 14, and 21 days and adult pigs. Whole kidney NOS I mRNA was greatest at birth and decreased progressively during renal maturation to adult levels. NOS I protein content paralleled this developmental pattern. Cortical NOS I protein was equivalent in newborn and 14-day-old piglets and was greater at both ages than the adult. Medullary NOS I protein was relatively greater than cortical in both immature ages and decreased from a peak at birth to adult levels. We conclude the following. 1) During postnatal maturation, renal NOS I mRNA and protein content show a pattern that is developmentally regulated. 2) This developmental pattern of NOS I after birth may, in part, contribute to the enhanced functional role of NO during renal maturation.

The influence of ketone bodies and glucose on interferon, tumor necrosis factor production and NO release in bovine aorta endothelial cells

Bovine aorta endothelial cells (BAECs) were used to determine the effect of ketone bodies and glucose on in vitro interferon (IFN), tumor necrosis factor (TNF) and nitric oxide (NO) production. BAECs were incubated for 4 and 24h with the ketone bodies: 3.8mmol/l beta-hydroxybutyrate (BHB), 1mmol/l acetoacetate (AcAc) and 5. 2mmol/l acetone (Ac), used separately or in a mixture together with cytokine inducers: Newcastle disease virus (NDV) and lipopolysaccharide (LPS). BHB alone (but not AcAc or Ac) and a mixture of ketone bodies caused a significant decrease in IFN titers induced by NDV and LPS and in TNF titers induced by LPS. Glucose used at concentrations of 5.55, 3.33 and 1.66mmol/l did not influence cytokine production.NO measured by the nitrite content in culture medium was released spontaneously from BAECs. A slight enhancement of NO release was observed after infection of BAECs with NDV; however, treatment with LPS caused inhibition of the release. The mixture of ketone bodies used with NDV or LPS enhanced NO release. However, when cells were incubated in the medium with 1. 66mmol/l glucose (mimicking low plasma glucose level in ketotic cows) a significant decrease in NO release was observed. This enhancing effect of ketone bodies and inhibition by low glucose in the final effect balanced each other, and the amounts of NO released in the medium with 1.66mmol/l glucose and with the mixture of ketone bodies resembled those produced at 3.33mmol/l glucose without ketone bodies. The significance of these effects of ketone bodies and glucose concentrations on cytokine and NO production in the immunity of ketotic cows has been discussed.

Distinct expression of splice variants of neuronal nitric oxide synthase in the human gastrointestinal tract

BACKGROUND & AIMS

Changes of neuronal nitric oxide synthase (nNOS) expression have been linked to several human gastrointestinal disorders such as achalasia, diabetic gastroparesis, and hypertrophic pyloric stenosis. They could be caused by differential transcriptional control or alternative splicing generating different nNOS proteins. The aims of this study were to characterize 5'-splice variants, promoter usage, and site-specific expression of nNOS in the human gastrointestinal tract.

METHODS

5'-Splice variants were characterized by immunoblotting, reverse-transcription polymerase chain reaction, 5'-rapid amplification of complementary DNA ends, and Southern blotting. Genomic analysis was performed by rapid amplification of genomic ends, followed by reporter gene assays.

RESULTS

Six different 5'-splice variants of nNOS-messenger RNA were identified showing specific expressions at various sites of the human gastrointestinal tract. Three variants encode for nNOSalpha, which has a specific N-terminal PDZ/GLGF domain and interaction sites for regulatory proteins. Two variants encode for nNOSbeta and 1 for nNOSgamma, which both lack the protein-binding domains of nNOSalpha. In addition to 2 known first exons, a novel first exon of human nNOS with a separate functionally active downstream promoter and multiple binding sites for transcription factors was identified and characterized.

CONCLUSIONS

Six 5'-mRNA splice variants of nNOS encoding 3 different nNOS proteins are expressed in the human gut. The differential expression of these proteins could be implicated in different biological functions.

Nitric oxide produced via neuronal NOS may impair vasodilatation in septic rat skeletal muscle

Impaired vascular responsiveness in sepsis may lead to maldistribution of blood flow in organs. We hypothesized that increased production of nitric oxide (NO) via inducible nitric oxide synthase (iNOS) mediates the impaired dilation to ACh in sepsis. Using a 24-h cecal ligation and perforation (CLP) model of sepsis, we measured changes in arteriolar diameter and in red blood cell velocity (V(RBC)) in a capillary fed by the arteriole, following application of ACh to terminal arterioles of rat hindlimb muscle. Sepsis attenuated both ACh-stimulated dilation and V(RBC) increase. In control rats, arteriolar pretreatment with the NO donors S-nitroso-N-acetylpenicillamine or sodium nitroprusside reduced diameter and V(RBC) responses to a level that mimicked sepsis. In septic rats, arteriolar pretreatment with the "selective" iNOS blockers aminoguanidine (AG) or S-methylisothiourea sulfate (SMT) restored the responses to the control level. The putative neuronal NOS (nNOS) inhibitor 7-nitroindazole also restored the response toward control. At 24-h post-CLP, muscles showed no reduction of endothelial NOS (eNOS), elevation of nNOS, and, surprisingly, no induction of iNOS protein; calcium-dependent constitutive NOS (eNOS+nNOS) enzyme activity was increased whereas calcium-independent iNOS activity was negligible. We conclude that 1) AG and SMT inhibit nNOS activity in septic skeletal muscle, 2) NO could impair vasodilative responses in control and septic rats, and 3) the source of increased endogenous NO in septic muscle is likely upregulated nNOS rather than iNOS. Thus agents released from the blood vessel milieu (e.g., NO produced by skeletal muscle nNOS) could affect vascular responsiveness.

Structure-activity relationship of staurosporine analogs in regulating expression of endothelial nitric-oxide synthase gene

In human umbilical vein endothelial cells and in human umbilical vein endothelial cell-derived EA.hy 926 cells, staurosporine (Stsp) and its glycosidic indolocarbazole analogs 7-hydroxystaurosporine (UCN-01) and 4'-N-benzoyl staurosporine (CGP 41251) enhanced nitric-oxide synthase (NOS) III mRNA expression (analyzed by RNase protection assay), protein expression (determined by Western blot), and activity [measured by rat fetal lung fibroblast (RFL-6) reporter cell assay] in a concentration- and time-dependent manner. In contrast, the bisindolylmaleimide analogs GF 109203X, Ro 31-8220 and Gö 6983 had no effect on NOS III expression, and Gö 6976, a methyl- and cyanoalkyl-substituted nonglycosidic indolocarbazole derivative of Stsp, even reduced NOS III expression in a concentration-dependent fashion. The up-regulation of NOS III expression by Stsp and analogs appears to be a transcriptional event because Stsp, 7-hydroxystaurosporine, and CGP 41251 enhanced the activity of a 1.6-kb human NOS III promoter fragment transiently transfected into EA.hy 926 endothelial cells. Stsp and analogs did not affect the stability of the NOS III mRNA. Stsp is known as a potent protein kinase (PK) inhibitor. Data obtained with other kinase inhibitors (and stimulators) indicated, however, that the effect of Stsp and analogs on NOS III expression was unrelated to the activities of PKC, PKA, PKG, or tyrosine kinase(s). Stsp analogs such as CGP 41251 also counteracted the NOS III mRNA-decreasing effect of tumor necrosis factor-alpha. These findings demonstrate that Stsp analogs represent a new class of compounds positively interacting with the transcription of the endothelial NOS III gene. Such compounds may prove useful in the prophylaxis and therapy of vascular disease.

Transcriptional and posttranscriptional regulation of endothelial nitric oxide synthase expression by hydrogen peroxide

Diverse stimuli, including shear stress, cyclic strain, oxidized LDL, hyperglycemia, and cell growth, modulate endothelial nitric oxide synthase (eNOS) expression. Although seemingly unrelated, these may all alter cellular redox state, suggesting that reactive oxygen intermediates might modulate eNOS expression. The present study was designed to test this hypothesis. Exposure of bovine aortic endothelial cells for 24 hours to paraquat, a superoxide (O(2)(-*))-generating compound, did not affect eNOS mRNA levels. However, cotreatment with paraquat and either Cu(2+)/Zn(2+) superoxide dismutase or the superoxide dismutase mimetic tetrakis(4-benzoic acid)porphyrin chloride increased eNOS mRNA by 2.3- and 2.2-fold, respectively, implicating a role for H(2)O(2). Direct addition of 100 and 150 micromol/L H(2)O(2) caused increases in bovine aortic endothelial cell eNOS mRNA that were dependent on concentration (ie, 3.1- and 5.2-fold increases) and time, and elevated eNOS protein expression and enzyme activity, accordingly. Nuclear run-on and 5, 6-dichloro-1-beta-D-ribofuranosylbenzimidazole-chase studies showed that H(2)O(2) caused a 3.0-fold increase in eNOS gene transcription and a 2.8-fold increase in eNOS mRNA half-life. Induction of eNOS by H(2)O(2) was not affected by the hydroxyl radical scavenger DMSO, mannitol, or N-tert-butyl-alpha-phenylnitrone, but it was inhibited by the antioxidants N-acetylcysteine, ebselen, and exogenously added catalase. Unlike H(2)O(2), the 4.0-fold induction of eNOS by shear stress (15 dyne/cm(2) for 6 hours) was not inhibited by N-acetylcysteine or exogenous catalase. In conclusion, H(2)O(2) increases eNOS expression through transcriptional and post-transcriptional mechanisms. Although H(2)O(2) does not mediate shear-dependent eNOS regulation, it is likely to be involved in regulation of eNOS expression in response to other physiological and/or pathophysiological stimuli.

Transcriptional induction of endothelial nitric oxide gene by cyclosporine A. A role for activator protein-1

We have previously shown that the immunosuppressant cyclosporine A (CsA) increases the activity, the protein level, and the steady-state levels of the mRNA of the endothelial nitric-oxide synthase (eNOS) gene in bovine aortic endothelial cells (BAEC). We have now investigated the mechanisms responsible for these effects. Preincubation with an inhibitor of RNA polymerase II abolished CsA-induced eNOS up-regulation. Nuclear run-on experiments demonstrated a 1.6-fold increase in the induction of eNOS gene by CsA. In agreement with these results, transient transfections showed that CsA augmented the transactivation of the eNOS promoter. Electrophoretic mobility shift assays showed an increase in the activator protein-1 (AP-1) DNA binding activity in BAEC treated with CsA. An increase in the level of c-fos mRNA and in the nuclear content of c-Fos protein was detected in BAEC treated with CsA. Site-directed mutagenesis of the AP-1 cis-regulatory element in the context of the human eNOS promoter resulted in the abrogation of the induction mediated by CsA. Hence, up-regulation of eNOS mRNA by CsA is a transcriptional phenomenon involving the proximal AP-1 site in the 5'-regulatory region of the human eNOS gene. Furthermore, our data exemplify how immunosuppressive drugs may result in the regulation of specific genes involved in the homeostasis of endothelial function, such as eNOS.

Variants of NOS1, NOS2, and NOS3 genes in asthmatics

Nitric oxide (NO) gas concentrations are higher in expired air in asthmatics. NO is synthesized by three isoforms of NO synthase (NOS) encoded by three distinct genes, NOS1, NOS2, and NOS3. Genome-wide searches have identified linkages to asthma on chromosomes 7, 12, and 17 where these three genes are localized. No association study, however, has been reported to date. To test whether variants of NOS1, NOS2, and NOS3 relate to asthma, a genetic association study was conducted in a British population (n = 300). Intragenic microsatellite variants of NOS1 were significantly associated with asthma [odds ratio (OR) = 2.08, 95% CI: 1.20-3.57 (95% CI), P = 0.008 (Pc = 0.048)], but not with IgE levels. Neither NOS2 nor NOS3 variants showed any association with asthma nor IgE levels. These findings suggest that NOS1 variants may be a significant contributor to asthma in a British population.

Nitric oxide synthase isoforms and glomerular hyperfiltration in early diabetic nephropathy

This study tested the hypothesis that nitric oxide (NO)-mediated renal vasodilation due to the activity of the inducible nitric oxide synthase (iNOS) contributes to glomerular hyperfiltration in diabetic rats. Two weeks after induction of diabetes mellitus by streptozotocin, mean arterial BP (MAP), GFR (inulin clearance), and renal plasma flow (RPF) (para-aminohippurate clearance) were measured in conscious instrumented rats. Diabetic rats had elevated GFR (3129 +/- 309 microl/min versus 2297 +/- 264 microl/min in untreated control rats, P < 0.05) and RPF (10526 +/- 679 microl/min versus 8005 +/- 534 microl/min), which was prevented by chronic insulin treatment. Intravenous administration of 0.1 and 1 mg of L-imino-ethyl-lysine (L-NIL), an inhibitor of iNOS, did not affect MAP, GFR, or RPF, either in diabetic or control rats. A higher L-NIL dose (10 mg) increased MAP and decreased RPF in diabetic rats significantly (n = 6, P < 0.05), but not in controls (n = 6). In addition, 0.1 mg of NG-nitro-L-arginine methyl ester (L-NAME), a nonselective blocker of NOS isoforms, decreased GFR (2389 +/- 478 microl/min) and RPF (7691 +/- 402 microl/min) in diabetic animals to control levels, while renal hemodynamics in normoglycemic rats were not altered. Higher L-NAME doses (1 and 10 mg) reduced GFR and RPF in diabetic and control rats to identical levels. In glomeruli isolated from diabetic and control rats, neither iNOS mRNA nor iNOS protein expression was detected. In contrast, increased protein levels of endothelial constitutive NOS (ecNOS) were found in glomeruli of diabetic rats compared with controls. By immunohistochemistry, ecNOS but not iNOS staining was observed in the endothelium of preglomerular vessels and in diabetic glomeruli. These results support the notion that increased NO availability due to greater abundance of ecNOS contributes to the pathogenesis of glomerular hyperfiltration in early experimental diabetic nephropathy. In contrast, we found no functional or molecular evidence for increased glomerular expression and activity of iNOS in diabetic rats.

Inactivation of zinc finger transcription factors provides a mechanism for a gene regulatory role of nitric oxide

Nitric oxide (NO) is known to induce Zn(2+) release from the zinc-storing protein metallothionein and to induce Zn(2+) release within the nuclei and cytoplasm of cells. This suggests that zinc finger proteins may be primary targets of NO-induced stress. In this study, the specific interaction of the heterodimeric complex of two zinc finger transcription factors, 1alpha,25-dihydroxyvitamin D(3) (1alpha,25(OH)(2)D(3)) receptor (VDR) and retinoid X receptor (RXR) with 1alpha,25(OH)(2)D(3) response elements (VDREs), was used as a model system. NO was applied to this system via the NO donors SNOC and MAMA/NO and caused a dose-dependent inhibition of VDR-RXR-VDRE complex formation (IC(50) values 0.5-0.8 mM). Ligand-bound or preformed complexes displayed less sensitivity to NO-induced stress. These in vitro effects of NO were found to be reversible. Functional assays in transiently transfected cells indicated that NO can also act in vivo as a repressor of 1alpha,25(OH)(2)D(3) signaling (IC(50) value of the slow NO donor DETA/NO, 0.5 mM). These findings suggest that NO has a modulatory role on transcription factors depending on their sensitivity to NO-induced stress, thus providing a mechanism for a gene regulatory function of NO.

Concerted actions of renal endothelial and macula densa NO systems in the maintenance of extracellular fluid volume

It is now clear that nitric oxide (NO) exerts a substantial influence on renal function and that the kidney has a high capacity to produce NO. However, there are at least two different NO systems in the kidney. The interplay between NO generated by the endothelium and by the macula densa is considered in this review. It seems that endothelial NO increases in response to an increase in perfusion pressure and an increase in distal delivery, whereas macula densa NO decreases upon a sustained increase in distal delivery. Furthermore, evidence is accumulating that macula densa NO may well mediate renin release. Though seemingly in contrast, both the response of the endothelial NO and of the macula densa NO system seem appropriate to restore a perturbation of fluid balance. The function of the tubuloglomerular feedback (TGF) mechanism is likely to be influenced by both sources of NO, because of the close proximity of these NO producing cells to the vascular smooth muscle cells of the afferent arteriole. The endothelial NO system seems to be responsible for short-term, dampening actions to increased afferent arteriolar tone elicited by activation of the TGF system. The macula densa NO system, on the other hand, is probably adapting TGF responses to sustained increases in distal delivery. The analysis presented in this paper is an attempt to integrate the function of the two NO systems into physiological regulation. The exact role of the medullary NOS enzymes remains to be further elucidated.

Production of nitric oxide by glial cells: regulation and potential roles in the CNS

Roles proposed for nitric oxide (NO) in CNS pathophysiology are increasingly diverse and range from intercellular signaling, through necrotic killing of cells and invading pathogens, to the involvement of NO in apoptosis and tissue remodeling. In vitro evidence and observations from experimental animal models of a variety of human neuropathologies, including stroke, indicate that glial cells can produce NO. Regulation of at least one of the NO synthase genes (NOS-2) in glia has been well described; however, apart from hints emerging out of co-culture studies and extrapolation based upon the reactivity of NO, we are a long way from identifying functions for glial-derived NO in the CNS. Although the assumption is that NO is very often cytotoxic, it is evident that NO production does not always equate with tissue damage, and that both the cellular source of NO and the timing of NO production are important factors in terms of its effects. With the development of strategies to transfer or manipulate expression of the NOS genes in specific cells in situ, the ability to deliver NO into the CNS via long-lived chemical donors, and the emergence of more selective NOS inhibitors, an appreciation of the significance of glial-derived NO will change.

Vascular biosynthesis of nitric oxide: effect on hemostasis and fibrinolysis

Nitric oxide (NO) is a multifunctional effector molecule that plays a central role in the regulation of vascular homeostasis. NO is synthesized from L-arginine by a family of enzymes called NO synthases. The principal source of NO in the vascular system of healthy mammals is the constitutively expressed NO synthase in endothelial cells. The basal endothelial formation of NO can be increased by receptor-dependent agonists (i.e., bradykinin) in a calcium-calmodulin-dependent manner, and also by physical forces (i.e., shear stress), predominantly without changes in the intracellular concentration of free calcium. Nitric oxide can diffuse toward the blood vessel wall where the major target is the smooth muscle cell. NO regulates vascular tone, and the free radical is also a potent inhibitor of smooth muscle cell proliferation, migration and synthesis of extracellular matrix proteins. NO can also diffuse toward the lumen of the blood vessel where it helps maintain blood fluidity. NO inhibits platelets' and leucocytes' adhesion to endothelial cells. In addition, NO inhibits platelet aggregation and facilitates the dissolution of small platelet aggregates. However, the regulatory action of NO on blood cells is most likely limited to the luminal surface of endothelial cells since NO is rapidly scavenged by hemoglobin in erythrocytes and inactivated by oxygen-derived radicals such as superoxide anions. NO can also affect the fibrinolytic activity by regulating the release of tissue-type plasminogen activator and plasminogen activator inhibitor-1. The crucial role of vascular NO in the control of blood fluidity has been demonstrated by the regulation of the bleeding time in humans.

Cystic fibrosis lung disease: the role of nitric oxide

This review summarizes current knowledge about the role of nitric oxide (NO) in cystic fibrosis (CF) lung disease. NO is endogenously produced by a group of enzymes, the NO synthases (NOSs). There are three isoforms of NOS, each encoded by different genes: neuronal (nNOS), immune or inducible (iNOS), and endothelial (eNOS) nitric oxide synthase.(1) They all form NO and L-citrulline by enzymatic oxidation of L-arginine. This reaction requires a number of cosubstrates, including molecular oxygen and tetrahydrobiopterin. It is now known whether all three isoenzymes are constitutively expressed in cells of the respiratory tract and that their gene expression is inducible.(2,3) NO production by iNOS, the "high-output" NOS, is stimulated by bacterial lipopolysaccharide (LPS) as well as proinflammatory cytokines such as interleukin (IL)-1gamma, IL-2, interferon (IFN)-gamma, and tumor necrosis factor (TNF). In contrast to nNOS and eNOS, activation of iNOS does not require an increase in intracellular Ca(2+) concentration.

Nitric oxide production during endotoxin-induced mastitis in the cow

Nitric oxide production was measured during endotoxin-induced mastitis. One hour after morning milking, the right hind quarters of 15 cows were infused with saline containing Escherichia coli endotoxin. Left hind control quarters were infused with saline only. At varying intervals before and after infusion, diagnostic markers of mastitis were recorded and nitric oxide production was evaluated by measuring nitrite plus nitrate levels in milk. In endotoxin-infused quarters, a significant increase in nitrite plus nitrate concentrations was observed 3 h postinfusion; concentrations decreased to preinfusion levels within 48 h. This change indicates that significant amounts of nitric oxide are released during endotoxin-induced mastitis. At 3 different time points, somatic cells were harvested from milk samples, plated, and maintained in culture for 24 h. The concentration of nitrite plus nitrate in medium from cells harvested 12 h postinfusion was increased, suggesting that nitric oxide is released, at least in part, by milk somatic cells. In a second set of experiments, we evaluated nitric oxide production when animals were infused with endotoxin and aminoguanidine, a specific inhibitor of the inducible form of nitric oxide synthase. In cows treated with aminoguanidine, the increase in nitrite plus nitrate observed after endotoxin infusion was prevented. These results suggest that nitric oxide production during endotoxin-induced mastitis resulted from the activity of the inducible form of nitric oxide synthase. They also support a possible involvement for nitric oxide in the inflammatory reaction observed during mastitis.

Estrogen stimulates neuronal nitric oxide synthase protein expression in human neutrophils

Recent studies have postulated the contribution of nitric oxide (NO) released by the endothelium to the beneficial effects of estrogen. Despite a neuronal-type NO synthase (nNOS) described in neutrophils, less is known about the effect of estrogen in these cells. The aim of the present study was to analyze the expression of nNOS protein in human neutrophils under different estrogenic conditions. We first analyzed nNOS expression in neutrophils obtained from premenopausal women. During the first 2 days of the follicular phase (low circulating estrogen concentrations), nNOS expression in neutrophils was reduced with respect to that found in neutrophils obtained from the same donors during the ovulatory phase (high circulating estrogen concentrations). Moreover, the expression of nNOS protein in neutrophils obtained from postmenopausal women after transdermal estrogen therapy was markedly enhanced with respect to that observed before the treatment. In vitro incubation of neutrophils derived from men for 6 hours with 17beta-estradiol (10(-10) to 10(-8) mol/L) upregulated the expression of nNOS protein. The 17beta-estradiol receptor antagonists, tamoxifen (10(-8) mol/L) and ICI 182780 (10(-8) mol/L), inhibited the upregulation of nNOS protein induced by 17beta-estradiol. The putative functional implication was denoted by a reduced expression of the CD18 antigen on the surface of 17beta-estradiol-incubated neutrophils, which was accompanied by a decreased adhesive capacity. Both effects were prevented by an NO antagonist. In conclusion, the in vivo levels of circulating estrogen concentrations seem to be associated with the level of nNOS protein expression in neutrophils from women. Moreover, low doses of 17beta-estradiol upregulate nNOS protein expression in neutrophils from men. The increased ability of 17beta-estradiol-incubated neutrophils derived from men to produce NO reduced their adhesive properties.

Down-regulation of the expression of endothelial NO synthase is likely to contribute to glucocorticoid-mediated hypertension

Hypertension is a side effect of systemically administered glucocorticoids, but the underlying molecular mechanism remains poorly understood. Ingestion of dexamethasone by rats telemetrically instrumented increased blood pressure progressively over 7 days. Plasma concentrations of Na(+) and K(+) and urinary Na(+) and K(+) excretion remained constant, excluding a mineralocorticoid-mediated mechanism. Plasma NO(2)(-)/NO(3)(-) (the oxidation products of NO) decreased to 40%, and the expression of endothelial NO synthase (NOS III) was found down-regulated in the aorta and several other tissues of glucocorticoid-treated rats. The vasodilator response of resistance arterioles was tested by intravital microscopy in the mouse dorsal skinfold chamber model. Dexamethasone treatment significantly attenuated the relaxation to the endothelium-dependent vasodilator acetylcholine, but not to the endothelium-independent vasodilator S-nitroso-N-acetyl-D,L-penicillamine. Incubation of human umbilical vein endothelial cells, EA.hy 926 cells, or bovine aortic endothelial cells with several glucocorticoids reduced NOS III mRNA and protein expression to 60-70% of control, an effect that was prevented by the glucocorticoid receptor antagonist mifepristone. Glucocorticoids decreased NOS III mRNA stability and reduced the activity of the human NOS III promoter (3.5 kilobases) to approximately 70% by decreasing the binding activity of the essential transcription factor GATA. The expressional down-regulation of endothelial NOS III may contribute to the hypertension caused by glucocorticoids.

Biochemical and functional characterization of nitric oxide synthase III gene transfer using a replication-deficient adenoviral vector

Nitric oxide (NO) produced in endothelial cells has been implicated in the regulation of blood pressure, regional blood flow, inhibition of platelet aggregation, and endothelial and vascular smooth muscle cell proliferation. In a variety of cardiovascular disease states, such as atherosclerosis, arterial hypertension, and restenosis, expression of endothelial NO synthase (NOS-III) and endothelial NO production appear to be altered. Thus, NOS-III is an attractive target for cardiovascular gene therapy for which adenoviral vectors are one of the most effective vector systems. Therefore, a recombinant adenoviral vector expressing NOS-III (adenovirus type 5 [Ad5] cytomegalovirus [CMV] NOSIII) was constructed and biochemically and pharmacologically characterized both in vitro and in intact cells. Ad5CMVNOSIII-derived recombinant NOS-III was successfully expressed, as shown by immunoprecipitation and immunocytochemistry, and biologically active, as shown by functional assays in human primary umbilical vein and EA.hy926 endothelial cells, as well as 293 human embryonic kidney and Chinese hamster ovary cells. The Km values for NADPH and L-arginine and the Ka for tetrahydrobiopterin as well as the enzyme's dependency on other cofactors were similar to recombinant reference enzyme and literature values. NOS-III expression levels correlated linearly with the multiplicity of infection with Ad5CMVNOSIII and lasted for at least 8 days. NOS-III transfection inhibited endothelial cell proliferation. In conclusion, adenovirus-mediated gene transfer of Ad5CMVNOSIII to vascular and nonvascular cells resulted in the dose-dependent expression of intact, physiologically regulated, and functionally active NOS-III.

Rheological influences on thrombosis

Blood flow plays important roles in the localization and morphology of thrombosis within the circulation. Blood flow properties (rheological variables) are associated with thrombotic risk factors and thrombotic risk; conversely their modification may reduce thrombotic risk.

Inhibitory activity of constitutive nitric oxide on the expression of alpha/beta interferon genes in murine peritoneal macrophages

We investigated the role of the constitutive nitric oxide (NO) in the expression of interferon (IFN) genes in mouse peritoneal macrophages (PM). The treatment of PM with L-arginine-N(G)-amine (AA), a potent inhibitor of NO-producing enzymes, resulted in a marked accumulation of IFN-alpha4 mRNA and, to a minor extent, of IFN-beta mRNA. In contrast, the expression of IFN-gamma mRNA, as well as tumor necrosis factor alpha and interleukin-6 mRNA, was not affected. Furthermore, a remarkable increase in the expression of the IFN regulating factor 1 (IRF-1), but not of IRF-2, mRNA was detected in AA-treated PM. To investigate whether the AA-induced activation of the IFN system correlates with the production and antiviral activity of IFN, the extent of encephalomyocarditis virus (EMCV) replication was monitored in AA-treated PM with respect to control cultures. AA treatment strongly inhibited, in a dose-dependent manner, EMCV yields in PM. Likewise, similar results were obtained by the addition of the NO-scavenger carboxyphenyl-tetramethylimidazoline-oxyl-oxide. In addition, inhibition of NO synthesis by N(G)-mono-methyl-L-arginine in PM strongly decreased virus replication in coculture of PM and EMCV-infected L929 cells, whereas no antiviral effect was observed in L929 cells alone. Moreover, the AA-mediated antiviral activity was abrogated in the presence of antibody to IFN-alpha/beta, whereas antibody to IFN-gamma was completely ineffective. Taken together, these results indicate that low levels of NO, constitutively released by resting PM, negatively regulate the expression and activity of IFN-alpha/beta in PM. We suggest that NO acts as a homeostatic agent in the regulation of IFN pathway expression in macrophages.

Type I nitric oxide synthase (NOS) is the predominant NOS in rat small intestine. Regulation by platelet-activating factor

Constitutive nitric oxide synthase (cNOS) may play an important protective role in the intestine, since our previous study has shown that the degree of bowel injury induced by platelet-activating factor (PAF), a potent inflammatory mediator, is inversely related to the cNOS content of the intestine. This study aims to examine the composition of the cNOS system in rat small intestine, and its regulation by PAF. We found that an approximately 120 kDa NOS I (neuronal NOS) is the predominant NOS in rat intestine, as evidenced by the following: (a) immunoblotting with specific antibodies detected a NOS I of approximately 120 kDa, but little NOS III; (b) the Ca(2+)-dependent, constitutive NOS (cNOS) activity of the rat intestine was removed by immunoprecipitation with the anti-NOS I, but not anti-NOS II or anti-NOS III antibodies; (c) RT-PCR revealed constitutive expression of NOS I in the intestinal tissue, but only a minute amount of NOS III. Immunofluorescent staining with anti-NOS I located NOS in the Auerbach plexus and nerve fibers in the muscle layer. We also found that this 120 kDa NOS I is rapidly (within 1 h) down-regulated in response to PAF administration. The protein level, enzyme activity as well as mRNA of nNOS were all decreased in the intestine.

Myofibroblasts. II. Intestinal subepithelial myofibroblasts

Intestinal subepithelial myofibroblasts (ISEMF) and the interstitial cells of Cajal are the two types of myofibroblasts identified in the intestine. Intestinal myofibroblasts are activated and proliferate in response to various growth factors, particularly the platelet-derived growth factor (PDGF) family, which includes PDGF-BB and stem cell factor (SCF), through expression of PDGF receptors and the SCF receptor c-kit. ISEMF have been shown to play important roles in the organogenesis of the intestine, and growth factors and cytokines secreted by these cells promote epithelial restitution and proliferation, i.e., wound repair. Their role in the fibrosis of Crohn's disease and collagenous colitis is being investigated. Through cyclooxygenase (COX)-1 and COX-2 activation, ISEMF augment intestinal ion secretion in response to certain secretagogues. By forming a subepithelial barrier to Na(+) diffusion, they create a hypertonic compartment that may account for the ability of the gut to transport fluid against an adverse osmotic gradient. Through the paracrine secretion of prostaglandins and growth factors (e.g., transforming growth factor-beta), ISEMF may play a role in colonic tumorigenesis and metastasis. COX-2 in polyp ISEMF may be a target for nonsteroidal anti-inflammatory drugs (NSAIDs), which would account for the regression of the neoplasms in familial adenomatous polyposis and the preventive effect of NSAIDs in the development of sporadic colon neoplasms. More investigation is needed to clarify the functions of these pleiotropic cells.

Interleukin-1beta-induced nitric oxide production in rat aortic endothelial cells: inhibition by estradiol in normal and high glucose cultures

Expression of inducible nitric oxide synthase (iNOS) and the resultant increased nitric oxide (NO) production are associated with septic shock, atherosclerosis, and cytokine-induced vascular injury. Estrogen is known to impact vascular injury and vascular tone, in part through regulation of NO production. In the current study, we examined the effect of physiological concentrations of estradiol on interleukin-1beta (IL-1beta)-induced NO production in rat aortic endothelial cells (RAECs). 17Beta-estradiol significantly decreased IL-1beta-induced iNOS protein levels and reduced NO production in RAECs. High glucose (25 mM) elevated the increase in IL-1beta-induced iNOS protein and NO production. Nevertheless, estradiol still inhibited IL-1beta-induced iNOS and NO production even in the presence of high glucose. These data suggest that estradiol may exert its beneficial effects in part by inhibiting induction of endothelial iNOS, a possible mechanism for the protective effect of estradiol against diabetes-associated cardiovascular complications.

Expression of the neuronal isoform of nitric oxide synthase (nNOS) and its inhibitor, protein inhibitor of nNOS, in pigment cell lesions of the skin

Nitric oxide (NO) is involved in many physiological processes. In cancer, low levels of NO are thought to enhance tumour progression and metastasis. NO is generated from arginine by NO synthase (NOS); the Ca2+-dependent neuronal isoform or nNOS (expressed by neurones and inhibited by the protein inhibitor of nNOS, PIN), is also expressed by cultured normal melanocytes and by all malignant melanoma (MM) cell lines. We studied the expression of nNOS and PIN in paraffin sections of 177 and 58 pigment cell lesions, respectively, using immunohistochemistry; the activity of the necessary cofactor NADPH was studied in 26 frozen cases. Normal melanocytes in situ lacked nNOS and PIN expression, but were NADPH +. Almost half of common acquired benign naevi expressed nNOS; however, halo naevi and congenital naevi expressed nNOS very frequently. Dysplastic naevi and MM showed variable nNOS immunoreactivity in 72% and 83% of cases, respectively. Early (Clark I and Clark II) MM displayed nNOS staining most frequently, and all MM with an invasive radial growth phase expressed nNOS in the papillary dermis. In contrast, only 67% of metastatic MM were nNOS +. PIN was coexpressed with nNOS in 40 of 58 lesions. NADPH activity was present in all nNOS + naevi, but in two malignant cases, NADPH activity was not accompanied by nNOS expression. We conclude that nNOS expression is induced de novo in benign and malignant pigment cell lesions which have all the requirements (NADPH, PIN) necessary for the production and modulation of NO. We postulate that the frequent expression of nNOS in the junctional part of dysplastic naevi may be responsible for their particular histological features. NO generated by the neoplastic dermal cells in the invasive radial growth phase may contribute to the increased number of blood vessels in the papillary dermis.